A typical mobile phone includes two microphones. Commonly, one of the microphones is positioned at a lower end of the mobile phone and configured to receive audio signals from a user when the mobile phone is in a normal mode during calls. Another microphone is positioned on a rear cover of the mobile phone and configured to receive the audio signal from the user when the mobile phone is in a hand-free mode during calls. However, when the mobile phone is placed on a desk with a screen facing upwards, the microphone positioned on the rear cover may be blocked and cannot effectively and stably receive the audio signals due to blocking. That may cause problem of volume and quality of the calls.